Fracture toughness, hysteresis and stretchability of dielectric elastomers under equibiaxial and biaxial loading

With the emergence of different dielectric elastomer transducers, the characterizations of dielectric elastomers are essential aspects for the design purpose. In this work, two potential dielectric elastomers, acrylic-based VHB and silicone-based Ecoflex, are tested and characterized under common loading conditions called equibiaxial and biaxial loading. Critical mechanical properties like hysteresis, fracture toughness, stretchability, and failure stress are obtained under equibiaxial and biaxial loading and compared with the same obtained under uniaxial and pure shear loading. It is found that hysteresis loss is almost equal in all three deformation modes. Fracture toughness under biaxial loading is more than that obtained from equibiaxial loading. Also, with increasing drawing ratio (DR), fracture toughness and failure stress decrease under biaxial loading condition. Stretchability is highest for uniaxial and followed by pure shear and equibiaxial loading cases. Stretchability is least for biaxial and with increasing drawing ratio, it further decreases. Fracture toughness, stretchability and failure stress are always more for VHB than Ecoflex under all deformation modes. However, hysteresis loss is more in case of VHB than Ecoflex. The present work successfully established the fact that for biaxial loading, fracture toughness and stretchability decreases drastically with drawing ratio. These results will provide the base of designing DEs transducers under various modes of deformation and more particularly for equibiaxial and biaxial deformation modes.